Lubricating oil composition



United States Patent" LUBRICATIN G OIL COMPOSITION William H. Brugmann, Jr., Milltown, N. J;,-assignor to Esso Research and Engineering-Company, a corporation of Delaware No Drawing. Original application June 29, 1950, Serial No. 171,250, now Patent No. 2,694,084, dated-Novemher 9, 1954. Divided and this application May 25, 1954, Serial No. 432,325

Claims. (Cl. 252-327) This invention relates to addition agents for improving the properties of mineral lubricating oil compositions, and relates more particularly to addition agents which impart detergent and oxidation inhibiting properties to engine lubricants.

The present application is a division of copending apfest in the maintenance of a clean engine during opera-' tion. Various metal compounds which have been used for such purposes include the metal derivatives of such organic compounds as fatty acids, naphthenic acids, petroleum sulfonic acids, alcohols, phenols, and ketones. However, these various metal compounds generally have the disadvantage of tending to corrode alloy bearings, such as those of cadmium-silver and copper-lead, now so widely used in automotive engines; and this is especially true in engines which operate at relatively high speeds and h gh temperatures. It is an object of the present invention to provide a new class of addition agents for oils which are to be used as crankcase lubricants, in which such agents exhibit the desirable properties of promoting general engine cleanliness, minimizing sludge formation, reducing ring sticking, piston skirt varnish formation, and the like, and at the same time are comparatively free from a tendency to cause corrosion of metal bearings.

'The new class of additives which have been found to meet the above requirements in a highly satisfactory manner are the neutral or basic metal salts of the products formed by reacting a di-organo-dithiophosphoric or di-organo-monothiophosphorous acid with a sulfonating agent. By neutral salt is meant a salt formed by reacting the sulfonated product with just a sufficient amount of'a metallic basic compound to replace all of the acid reacting hydrogen atoms of the product with a metal. A basic salt is one containing more than this amount of metal. The salts may be formed by a neutralization reaction or by double decomposition of one metal salt with another metal salt. The organic groups of the acid of phosphorus are hydrocarbon groups containing from 3 to carbon atoms each, which may be alkyl groups, whether saturated, or unsaturated, straight chain or branched, or they may be alkaryl or aralkyl groups containing at least 2 carbon atoms in a side chain. The sulfonating agent employed may be any sulfonating agent, such as fuming sulfuric acid, chlorosulfonic acid, fluorosul-fonic acid, a sulfur trioxidedioxane complex in ethyl ethersolution, and similar agents. The sulfonation reaction is exothermic andis accomplished by merely contacting the reagents under controlled temperature conditions, the most suitable temperature having been found tube of theorder of -40 to 15 C.,.and the best yields are generally obtained at temperatures not higher than 0' 2,786,029 Patented Mar. 19, 1957 ice C. It is generally preferable to employ from 1 to 2.5 mols of the sulfonating agent for each mol of the phosphorus-containing acid, although on occasion higherproportions of the sulfonating agent may be used. An inert solvent is preferably employed such as a liquid sulfur dioxide, dioxane, or a saturated liquid aliphatic hydrocarbon, e. g., hexane.

As examples of suitable dithiophosphoric acids may be mentioned di-n-propyl dithiophosphoric acid, di-isobutyl dithiophospori-c acid, di-n-hexyl dithiophosphoric acid, di-n-octyl dithiophosphoric acid, di-Z-ethylhexyl dithiophosphoric acid, di-tert.-oct yl dithiophosphoric acid, dilauryl dithiophosphoric acid, di-isobutylphenyl dithiophosphoric acid, dioleyl dithiophosphoric acid, diethylphenyl dithiophosphoric acid, di-tert.'-oc,tylphenyl dithiophosphoric acid, di-diamylphenyl dithiophosphoric acid, di-phenylethyl dithiophosphoric acid, and similar compounds. The corresponding monothiophosphorous acids are equivalent for the purposes of the present invention. The oregano-substituted acids of phosphorus-may be readily formed by reacting an alcoholor phenol with a sulfide of phosphorus, e. g. P283, P285, P483, or P487, by methods well known to the art.

Among the alcohols which are generally preferred for use as starting agents in the preparation of the monothiophosphorous or dithiophosphoric acids which are sulronated and converted into metal salts in accordance with the present invention may be mentioned ethyl, isopropyl, amyl, Z-ethylhexyl, lauryl, stearyl, and methyl-cyclohexyl alcohols, as wellascommercial mixtures of alcohols, such as the mixture of alcohols essentially ofthe C10 to C18 range derived from coconut oil and known as Lorol 13 alcohol. Other naturalproducts containing alcohols such as the alcohols derived from wool fat, sperm oil, natural waxes and the like, and alcohols produced by the oxidation of petroleum hydrocarbon products, also the 0x0 alcohols produced from olefins, carbon monoxide and hydrogen, may likewise be employed. Aromatic compounds such as alkylated phenols of the type of n-butyl phenol, tert.-amyl phenol, diamyl phenol, tert.-octyl phenol, cetyl phenol, petroleum phenol, and the like, as well as the corresponding naphthols, may be employed in like manner.

The metals which are employed for the neutralization of the sulfonated product may be any metals, but the alkali and alkaline earth metals are preferred. Among other metals, magnesium, zinc, tin, copperandlead may be especially mentioned. The usual basic metal compounds, such as oxides, hydroxides, and carbonates, may be employed in the neutralization reaction.

No formula or other indication of the exact structure of the compounds resulting from the above described reactions is given, since from the analyses of the products it has not been found possible to determine whether the sulfonate group becomes attached to one of the organic. groups of the acid of phosphorus, or whether the sulfhydryl groups of. the acid is converted into a S.SO3H group. There .is also. the .possihility'that a portion of the acid may become. converted into the: corresponding disulfide compound by elimination of the hydrogen under the oxidizing influence of the sulfonating agent.

The amount of the additives of the present invention which are to be employed in mineral lubricating oil compositions will normally range from about 0.02 to about 5%, and the particular amount in individual caseswill be selected in accordance with the requirements of the case and in view of the properties of the base stock employed. For commercial purposes, it is convenient to prepare concentrated oil solutions in which the amount of additive in the composition ranges from 25% to 50% by weight, and to transport and store them in such EXAMPLE I Preparation of additive 1 molecular proportion (117 g.) of chlorsulfonic acid was added over a period of /2 hour to an equal molecular proportion (354 g.) of di-Z-ethylhexyl dithiophosphoric acid dissolved in 200 cc. of liquid sulfur dioxide, while maintaining a temperature of -23 to 17 C. The sulfur dioxide solvent was then flashed ofi, and the product (200 g.) was blended with 689 g. of a solvent extracted Mid-Continent type lubricating oil stock derived from a Panhandle crude and having a viscosity (Saybolt) of 43.8 seconds at 210 F. and 160.5 seconds at 100 F. and a Dean and Davis viscosity index of about 100. This blend was then treated at 120-125 C. with 218 g. of Ba(OH)2.8HzO. The final concentrate in oil contained about 20% by weight of product. The neutralized oil concentrate was filtered through Hy-flo (a filter-aid), the product being a clear, light colored oil. Analysis of this product gave the following results:

Percent Phosphorus 1.05 Sulfur. 2.42 Barium 2.50

Neutralization No. 0.1 alkaline.

EXAMPLE II Preparation of additive 1.03 molecular proportions (121 g.) of chlorsulfonic acid was added over a period of minutes to 0.565 molecular proportions (200 g.) of di-Z-ethyhexyl dithiophosphoric acid dissolved in 300 cc. of liquid sulfur dioxide, while maintaining a temperature of 40 to 29 C. The mixture was then stirred for one hour at 37 to l8 C. to insure complete reaction. The sulfur dioxide solvent was then flashed off and the product was blended with 800 g. of the same type of lubricating oil solvent that was used in Example I. then treated at 80 to 90 C. with 356 g. (1.13 molecular proportions) of Ba(OH)2.8HzO, While bubbling nitrogen through the mixture. An antifoam agent was added and the temperature raised to 150 C. The product was then filtered through Hy-fio. The final product contained about 32% by weight of the barium salt. Analysis .of this product gave the following results:

Percent Phosphorus 1.42 Sulfur 2.70 Barium 5.71

Neutralization No. 4.75 alkaline.

- EXAMPLE III Laboratory bearing corrosion test This blend was in inhibitiing the corrosiveness of a typical mineral lubrieating oil towards the surfaces of copper-lead bearings. The test-was conducted as follows:

500 cc. of the oil was placed in a glass oxidation tube (13 inches long and 2% inches in diameter) fitted at the bottom with a inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automative bearings of copper-lead alloy of known weight having a total .area of 25 sq. cm. were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing sufiicient agitation of the sample during the test. Air was then blown through the oil at the rate of 2 cu. ft. per hour. At the end of each four-hour period the bearings were removed, washed with naphtha and weighed to determine the amount of loss by corrosion. The bearings were then repolished (to increase the severity of the test), reweighed, and then subjected to the test for additional four-hour periods in like manner. The results are given in. the following table as corrosion life, which indicates the number of hours required for the bearings to lose mg. in weight, determined by interpolation of the data obtained in the various periods:

Bearlng' Oil or Oil Blend Corrosion Lite (Hrs) Base oil Base oil-l-product of Example I. 27 Base oil-i-product 0t Example 11 l6 EXAMPLE IV Lauson engine test Blends containing 10% by weight of the concentrate of Example I and 6.65% of the concentrate of Example II (2% by weight of the active ingredient in each case) in a solvent extracted coastal naphthenic oil of 60 sec onds (Saybolt) viscosity at 210 F. and a sample of the unblended base oil were employed as the crankcase lubricants in tests with a Lauson engine operating at 295 F. jacket temperature and 300 F. oil temperature, 1800 R. P. M. speed, and 1.5 indicated kilowatt load, the tests being conducted for 25 hours each. The loss in weight of the copper-lead bearing and the varnish demerit were determined in each case. The varnish demerit rating was based upon a method of rating in which a perfectly clean piston surface had been given a rating of 0 and a demerit rating of 10 was given to the worst condition which could be expected to exist on that surface. The results of these observations are as follows:

Bearing Lubricant Varnish Weight Demerlt Loss (mg./

bearing) Base 011 G. 00 06 Base 011+ product of Example 1.- 2. 50 2t Base oil product of Example II 1. 75 5 It will be seen from the above data that the additive not only exhibited a detergent effect in lowering the var- I nish deposits on the piston surface but reduced the amount of corrosion on the bearing to a substantial degree. l The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in ithefheavy duty type of lubricating oils which. have been compounded with such detergent type additives as metal soaps, metal petroleum sulfonates, metal phenates,

metal alcoholates, metal alkylphenol sulfides, metal 'or- 'gano phosphates, phosphites, .thio phospha-tes."andfmidphosphite's, guanidine" salts, metal xa'nthates and'thioxam thates, metal thiocarbamates, and the like. Other types of additives, such as phenols and phenol sulfides, may also be present.

The lubricating oil base stocks used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from parafiinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constitutents have been carefully removed. The oils may be refined by conventional methods using .acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced by solvent extraction with solvents such as phenol, sulfur dioxide, etc. Hydrogenated oils or white oils may be employed as well as synthetic oils such as polyester or polyglyool type oils, or those prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products. In certain instances cracking coil tar fractions and coal tar or shale oil distillates may also be used. Also, for special applications, animal, vegetable or fish oils or their hydrogenated or voltolized products may be employed in admixtures with mineral oils.

For the best results the base stock chosen should normally be an oil which with the new additive present gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their use also makes feasible the employment of less satisfactory oils, no strict rule can be laid down for the choice of the base stock. The additives are normally sufficiently soluble in the base stock, but in some cases auxiliary solvent agents may be used. The lubricating oils will usually range irom about 35 to 150's'econds Say-bolt viscosity at 210 F. The viscosity index may range 0 to 100 or even higher.

Other agents than those which have been mentioned may be present in the oil composition, such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, and the like.

'Assisting agents which are particularly desirable as plasticizers and defoamers are the higher alcohols having preferably 8-20 carbon atoms, e. g., octyl alcohol, lauryl alcohol, stearyl alcohol, and the like.

In addition to being employed in crankcase lubricants, the additives of the present invention may also be used in extreme pressure lubricants, engine flushing oils, industrial oils, general machinery oils, process oils, rust preventive compositions and greases.

What is claimed is:

1. A mineral lubricating oil composition comprising a major proportion of a mineral lubricating oil containing dissolved therein about 0.02% to about 5% of a nonacidic metal salt of the product formed by reacting one molecular proportion of an acid of phosphorus of the formula the formula is an alkyl radical.

5. A composition according to claim 1 in which -R of the formula is a Z-ethylhexyl radical.

6. A composition according to claim 1 in which the sulfionating agent is chlorsulfonic acid.

7. A mineral lubricating oil containing dissolved therein 0.02 to about 5% of the non-acidic barium salt of the product formed by reacting di2-ethylhexyl dithiophosphoric acid with an equal molecular proportion of chlorsulfonic acid at a temperature of 40 to 15 C.

8. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor atleast oxidation inhibiting proportion of a non-acidic metal salt of the product formed by reacting one molecular proportion of an acid of phosphorus'of the formula where R is a hydrocarbon radical containing 3 to 30 carbon atoms and having at least one open chain aliphatic hydrocarbon group containing at least 2 carbon atoms with from one to two and one-half molecular proportions of a sulfonating agent at a temperature of about -40 to 15 C.

9. A composition according to claim 8 in which said lubricating oil comprises at least a lubricating proportion of a mineral oil.

10. A composition according to claim 8 in which said proportion is about 0.02 to about 5% byweight of said composition.

11. A composition comprising at least about by weight of a lubricating oil and about 25-50% by weight of a non-acidic metal salt of the product formed by reacting one molecular proportion of an acid of phosphorus of the formula where R is a hydrocarbon radical containing 3 to 30 carbon atoms and having at least one open chain aliphatic hydrocarbon group containing at least 2 carbon atoms with from one to two and one-half molecular proportions of a sulfonating agent at a temperature of about --40 to 15 C.

12. A composition according to claim 11 in which said lubricating oil comprises at least a lubricating proportion of a mineral lubricating oil.

13. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor at least oxidation inhibiting proportion of the non-acidic barium salt of the product formed by reacting di-2-ethylhexyl dithiophosphoric acid with an equal molecular proportion of chlorsulfonic acid at a temperature of 40 to 15 C.

14. A composition according to claim 13 in which said minor proportion is about 0.02 to about 5% by weight of said composition. 7

15. A composition according to claim 13 in which said lubricating oil comprises at least a lubricating proportion of a mineral lubricating oil.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A MINERAL LUBRICATING OIL COMPOSITION COMPRISING A MAJOR PROPORTION OF A MINERAL LUBRICATING OIL CONTAINING DISSOLVED THEREIN ABOUT 0.02% TO ABOUT 5% OF A NONACIDIC METAL SALT OF THE PRODUCT FORMED BY REACTING ONE MOLECULAR PROPORTIONS OF AN ACID OF PHOSPHORUS OF THE FORMULA 